This invention relates to a novel photographic coupler which is used as a color photographic material, more specifically to a photographic coupler which forms a dye image excellent in fastness to heat, humidity and light.
By subjecting a light-sensitive silver halide photographic material to exposure and then color development processing, an oxidized aromatic primary amine color developing agent and a dye-forming coupler are reacted in an exposed area to form a dye, whereby a color image is formed.
In such a photographic method, a color reproduction method according to a subtractive color system is generally used, and yellow, magenta and cyan color images are formed.
As a photographic coupler used for forming the above yellow color image, there may be mentioned, for example, an acylacetanilide type coupler. As a coupler for forming the magenta color image, there has been known, for example, a pyrazolone, pyrazolobenzimidazole, pyrazolotriazole or indazolone type coupler. Further, as a coupler for forming the cyan color image, there may be generally used, for example, a phenol or naphthol type coupler.
The dye image thus obtained has been demanded to be neither discolored nor faded even if it is exposed to light for a long time or stored at high temperature and high humidity.
However, a phenol type coupler and a naphthol type coupler which have been studied as a coupler for forming a cyan dye are not so satisfactory in the points of spectral absorption characteristics, heat resistance, humidity resistance and light resistance of a cyan dye image formed. For improving these properties, various proposals including change of substituents have been made. For example, a 2,5-diacylphenol type cyan coupler has been disclosed in Japanese Provisional Patent Publication No. 31953/1984; a two-equivalent type naphthol cyan coupler has been disclosed in Japanese Provisional Patent Publications No. 117422/1975 and No. 32071/1980; a cyan coupler having an ureido group at the 2-position of phenol has been disclosed in Japanese Provisional Patent Publication No. 65135/1981; and a cyan coupler having an acyl group at the 5-position of naphthol has been disclosed in Japanese Provisional Patent Publication No. 53643/1986. However, a compound which is satisfactory in all these properties has not yet been obtained.